Method of preparing resinous linear polyesters in crumblike form



Patented Nov. 23, 1948 METHOD F PREPARING RESINOUS LINEAR POLYESTERS INCRUMBLIKE FORM Ellington M. Beavers, Philadelphia, Pa... designer toRohm & HaasCompany, Philadelphia, Pa... a corporation of Delaware NoDrawing.

Application November 23, 1045, Serial No. 630,580

8 Claims. (Cl. 260-75) This. invention relates to millable, mcldable,crumblike, non-crystalline, curable, thermoplastic -mlyester materialsand to a process of preparing same. The millable character of thesepolyesters permits ready compounding with tillers. curin agents,modifiers, pigments, and the like, to an extent not heretofore possible.The crumblike term of the polyesters permits ready handling, packaging,shipping, and storing. Polyesters heretoioreevailable were deficient inthese respects, and the object of this invention is to produce newpolyesters in such a physical form that they may be convenientlyutilized and that full advantage may be taken or their outstandingchemical characteristics.

These new polyesters are prepared by mechanically working and heating amixture of a polyester and a peroxidic catalyst in an amount from about0.055% to about 0.0025%. based on the poll'- ester, until the mixture isconverted into a crumblike mass. The product, which is stillthermoplastic, can be easily handled, milled, and molded.

The Polyesters which are employed herein are non-crystalline linearpolyesters of relatively high molecular weight containing alternatechains from dicarboxylic acids and a dihydrlc alcohol, the latter havinga chain length of at least two carbon atoms and having hydronyl groupsas the sole reactive functional. groups, the chains from thedicarboxylic acids in the linear polyesters con--- sisting of a majorproportion of chains from a saturated dicarboxylic acid having; a chainlength of at least four carbon atoms and carbonyl sroups as the solereactive functional groups and simmer proportion of chains from ansip-unsaturated dicarboxylic acid.

conversion of the two-dimensional linear polyesters to thethree-dimensional form ordinarily takes place during the moldingoperation and is commonly referred to as "curing."

The thoroughly "cur-ed polyesters are substantially insoluble andinfusible and are very similar to vulcanized rubber. They are, in fact,synthetic elastomers characterized by resiliency, elasticity, andflexibility. Despite the fact that such desirable rubber-like productswere heretoiore known to be potentially available from unsaturatedlinear polyesters, the latter have not enjoyed wide commercialacceptance because of the difliculties previously encountered inhandling and in the milling and the curing operations to which they hadto be subjected. 0n the other hand, 'the'products of this invention, intheir crumblike, thermoplastic form, can be utilized to excellentadvantage;

The preferred method or manufacture of the polyesters which are employedin this invention comprises heating the saturated dicarboxyiic acid, theunsaturated dicarboxylic acid, and an excess or a sly col under reducedpressure in the presence ship and which is inherently deficient inmilling The polyesters are prepared by the esterif ication of anunsubstituted dihydric alcohol. such as l,2 -propylene glycol, asaturated, unsubstituted, aliphatic dicarboxylic acid. such as schools.acid, and an unsaturated afi-dicarboxylic acid such as maieic. Theseesters are essentially of the linear or two-dimensional type and arepartially unsaturated due to the presence of the double bond in theresidue oi the esterifled unsaturated acid. The double bonds impartthermosettlng properties to the polyesters, which can, therefore,cross-link, under the influence of heat and/or a catalyst, at the doublebonds to form three-dimensional polymers which are no longerthermoplastic. The

and/or molding properties, is placed in a power mixer, such as aWerner-Pileiderer. A small amount of peroxidic catalyst is added,preferably at a temperature from about 50 C. to about C. Polymerization,induced by the heat and catalyst, begins and is exothermic. The mixtureis maintained at a temperature of 50 C. to about 150 C., and preferablybetween C. and C. After the mixture is simultaneously heated and workeda short time, the resinous, stickypolyester is converted into a slightlytacky, crumbly mass which can be droppeddirectly from the mixer intoshipping containers or transferred directly to milling rolls. It handleswell and can be weighed, packaged, and'transported without diiiiculty.Moreover, in the crumblike form, the

not suitable as elastomers.

polyester mills far more readily than the original material from whichthe crumb was prepared. At the same time, the crumblike product isthermoplastic, it flows readily when heated and pressed. and can bemolded with ease.

The polyesters which are involved herein are those which arenon-crystalline and which have a molecular weight above 5000. By"non-crystalline" polyesters is meant those which at normal roomtemperature do not display a regular X-ray pattern and cannot becold-drawn. Non-crystallinity results from the failure of the moleculesto fall into aregular space lattice. One way of assuring that themolecules do not fall into such a lattice is to employ either a dihydricalcohol or a dibasic acid, preferably the former, which has a sidechain. For example, 1,2-propylene glycol, with its methyl group forminga side chain, produces non-crystalline polyesters, whereas its isomer,Lil-propylene glycol, produces microcrystalline polyesters, all otherfactors remainin the same. This invention is limited to the polyestersof the. non-crystalline or non-microcrystalline type.

In addition to the non-crystalline character of the polyesters, theirmolecular weight is also of prime importance. weight of 5000 isrequired, the maximum value may be as high as 50,000. It is preferred,however, that the molecular weight be between 10,000 and 30,000. Unlessthe molecular weight is above 5000, the molded products thereof are Themolecular weight may be conveniently estimated from viscositymeasurements and the use of Staudingers well known formula forcalculating molecular weight from viscosity data as given in his bookDie Hochmolekularen Organishen Verbindungen (1932, Berlin).

Suitable dihydric alcohols are those which are saturated and which donot contain groups, other than the hydroxyl groups, which are reactiveunder the conditions employed in making linear polyesters therewith.Such alcohols are conveniently described as being unsubstituted and maybe exemplified by ethylene glycol, 1,3-propylene glycol, 1,2-propyleneglycol, butylene glycol, diethylene glycol, dipropylene glycol,hexamethylene glycol, and the like. Mixtures of glycols' are alsooperable, as, for example, a mixture of ethylene glycol and1,2-propylene glycol.

The dicarboxylic acids which are preferred are those saturated aliphaticacids having at least two carbon atoms between the carboxyl groups, or astraight chain length of at least four carbon atoms including the carbonatoms of the carboxyl groups. Furthermore, the dicarboxylic acids offirst choice do not contain any groups. other than the carboxyl groups,which are reactive under the conditions employed in the formation of thelinear polyesters. They may be described as unsubstituted, and the word"unsubstituted is used in that sense here and elsewhere throughout thisspeciflcation. Thus;

succinic, adipic. a-methyl glutaric, pimelic, suberic, azaleic, sebacic,and higher acids may be used. Sebacic acid is particularly satisfactory,especially in conjunction 'with 1,2-propylene glycol and maleicanhydride. Mixtures of acids, such as a mixture of sebacic and adiplcacids, may alsobe employed.

Suitable nip-unsaturated dicarboxylic acids are those which areunsubstituted and which combine. as do the saturated dicarboxylic acids,to form linear polyesters, made up of alternate While a minimummolecular 4 esteriiled residues of the dicarboxylic acids and thedihydric alcohol. Included as operable are maleic, fumaric, citraconic,and mesaconic acids. Maleic acid is preferred and may be used in theform of its anhydride or a lowerv aliphatic ester which reacts bytransesteriflcation. The amount of, unsaturated acid which is used has amarked eifect upon the properties of the polyester. As indicated above,the presence in the polyester of the double bond in the residue of theesterifled unsaturated acid imparts to the resin the capacity forforming cross-linkages," resulting in conversion to three-dimensionalpolymers. ,It is convenient and customary to express the amount ofunsaturated acid as a molar percentage of the total acids present. andthis system has been adopted herein. The amount of unsaturated acid usedwill depend largely upon the properties to be attained in the finishedpolyester and somewhat upon the conditions of operation. In a generalway, the maximum molecular weight obtainable in a substantially linearpolyester, other factors being contant, will vary inversely with theamount of unsaturated acid employed. In cases where a polyester ofextremely high molecular weight is prepared, the amount of unsaturatedacid employed is very low and.

may be as low as 0.1%. However, the. amount ordinarily used is aboveabout 1%. The maximum amount contemplated is about 20%. For mostapplications, an amount between about 1% and about 6% is much preferredbecause this proportion of unsaturated acid assures a sumciently highdegree of unsaturation in the polyester to permit cross-linking and alsopermits the esteriflcation to proceed until the product has asufliciently high molecular weight, for example, between about 5000 andabout 50,000 and preferably between about 10,000 and 30,000.

Examples of peroxidic curing catalysts which may be used in theconversion of the resinous polyester to the crumblike condition-areinorganic peroxides, such as'barium and sodium peroxides, and the moresatisfactory organic agents such as acetyl peroxide, lauryl peroxide,stearyl peroxide, tert.-butyl hydroperoxide, benzoyl peroxide,tert.-butyl perbenzoate, di-tert.'- butyl diperphthalate, di-tert.-butylperoxide, and the barium salt of tert.-butyl hydroperoxide.

In the case of those polyesters containing the lower limit of about 1%of unsaturated acid. about 0.033% to about 0.055% of catalyst, based onthe weight of the linear polyester, is required in the crumb-formingoperation. In the case of the polyesters containing the maximum amount,20%, of unsaturated acid, the required amount of catalyst'is much lessand is in the range of about 0.0025% to about 0.015%, based on thepolyester. Polyesters containing intermediate amounts of unsaturatedacid require amounts of catalysts between the limits given above. Thereis a straight-line relationship between the required amount of catalystand the percentage of unsaturated acid employed in manufacture of thepolyester.

From a practical standpoint, the amount of catalyst required is thatwhich produces a slightly tacky, millable, and moldable crumb when 4 thelinear polyester is mechanically worked and heated at temperatures of50-160 C., and preferably C. to..150 C. The crumb is millable when itknits together to form a band on being fed into a roller mill. Crumbswhich are-too highly cured drop through the rollers without .lmittingtogether and, hence, are not millable.

, this invention:

Example 1 Que thousand grams of a linear polyester havina a molecularweight 01' about 15,000andprepared lrom 1,2-propylene glycol, sebacicacid, and maleic acid, the acids being present in a ratio oi 07:3 on amolar basis, was placed in a laboratory-size Werner-Pfleiderer mixer.The polyester was worked and simultaneously heated to 75 C. A slowstream of carbon dioxide comprises simultaneously mechanically worklniin a power mixer oi the kneading type and heating, at 50 C. to 150 C.until a crumb is formed, a mixture oia peroxidic curing catalyst and alinear, unsaturated, thermoplastic non-crystalline polyester molecularweight of 5000 to 50,000,

said ester being the product of condensing by heating together asaturatedunsubstituted glywas directed against the surface 0! thepolyester in order to prevent oxidation. At the elevated temperature,0.045% of benzoyl peroxide, based on the weight oi the polyester and inthe form of a 20% solution in chlorolorm, was added. Heatinc and workingwere continued ior fifteen minutes, and, during this time, the stickyresinous polyester changed to a very slightly tacky, crumbly mass. Thecrumb was dropped from the mixer. it was then transferred to a coldrubber mill and was milled very readily and rapidly to a sheetresembling pale crepe rubber. This sheeted product was then compoundedon the rubber mill with iron oxide and 1%, based on the polyester, oibenaoyl peroxide. Portions were then molded in a standard A. S. T. M.mold at 20 pounds per square inch steam pressure for ten minutes. Thereresulted a rubber-like slab which completely reproduced the contours ofthe mold. It was resilient and elastic and had a bend-brittle point oi-52 C.

Example 2 Twelve hundred twenty-five grams oi a substantially linearpolyester having a molecular weight of about 10,000, and prepared frometh= ylene glycol, 1,2-propylene alycol, sebacic acid, and maleicanhydrlde, the alycols being present in a ratio oi 00:20 on a weiahtbasis and the ratio of sehacic acid to malelc anhydrlde heina" $0220 ona molar basis, was placed in a mixer and was simultaneously heated andworked at a temperature oi 60 C. Tertiary butyl hydroper= oxide, in anamount equal to .0075% or the weight oi the polyester, was added.Heating and workins; continued, and the temperature rose rapidly toabout 110 C. and was maintained between 100 C. and 120 C. After aworking and heatthe period oi fifteen minutes, the polyester was incrumb form and had excellent milling characteristics as contrasted witha portion oi the same polyester which had not been subjected to theabove treatment.

The process of this invention, which relates to improvements in themilling and molding qualities of curable, non-crystalline, linearpolyesters of molecular weight above about 5000, is very valuablecommercially because it has made it possible to produce syntheticelastomers with a minimum of effort from linear polyesters tormerlybelieved to have, at best, only limited utillty. I claim: 1. A processoi preparing millable, moldable, crumblike, curable thermoplasticmaterial which col, a saturated unsubstituted dicarboxylic acidcontaining a minimum of four carbon atoms, and an unsubstitutedaye-unsaturated dicarboxylic acid, said unsaturated acid being presentin an amount from 1% to 20% of the total acids on a molar basis, one oisaid slycol and said saturated acid containing a branched chain, andsaid peroxidic curing catalyst being present in an amount from 0.055% to0.0025%, based on said polyester, and being inversely proportional tothe percentage of said unsaturated acid used.

2. A process of preparing millable, moldable, crumbllke, curablethermoplastic material which comprises simultaneously mechanicallyworking in a power mixer oi the kneadlns type and heating, at 50 C. toC. until a crumb is formed,

- a mixture of a peroxidic curing catalyst and a linear, unsaturated,thermoplastic non-crystalline polyester of molecular weight oi 10,000 to30,000, said ester being the product of condensing by heatins together asaturated unsubstituted glycol, a saturated unsubstituted dicarboxylicacid containing a minimum of four carbon atoms, and maleic acid, saidmaleic acid being present in on amount lrom 1% to 20% oi the total acidson a molar basis, one of said glycol and. said saturated acid containinga branched chain, and saidperouidic curina, catalyst being present in anamount from 0.055% to 0.0025%, based on said polyester, and beinginversely proportional to the percentage of said maleic acid used.

3. A process of preparing millable, moldable, crumblike, curablethermoplastic material which comprises simultaneously mechanicallyworking in a power miner oithe kneadina type and heatinc,.at 50 G. to150 C. until a crumb is formed, a mixture of a perouldic curing;catalyst and a linear, unsaturated, thermoplastic non-crystal linepolyester oi molecular weight at ilttilil to 50,000, said ester loelnathe product oi condensing by heating together l,2=propylenc glycol,aehaclc acid, and motels acid, said nucleic acid being present in anamount tram l% to 20% oi the total acids on a molar basis and saidcuriae cata= lyst being present in an amount irons 0.005% to 0.0025%,based on said polyester, and said amount losing inversely proportionalto the peroentase of said nucleic acid used.

a. A process at preparing millable, moldahle, crumblihe, curablethermoplastic material which comprises simultaneously mechanicallyworking in a power mixer ol the kneading type and heatinc, at 50 C. to150 C. until a crumb is :i'ormed, a mixture at an organic peroxidiccuring catalyst and a linear, unsaturated, thermoplastic noncrystallincpolyester of molecular weight of 10,000 to 30,000, said ester helps theproduct 01' condensing by heating together l,2-propylene glycol, sebacicacid, and maleic acid, said maleic acid being present in an amount irom1% to 0% of the total acids on a molar basis and said or-- ganic curingcatalyst being present in an amount from 0.055% to 0.0025%, based onsaid polyester,

and said amount being inversely proportional to the percentage of saidmaleic acid used.

5. A new composition of matter comprising a millable, moldable,crumblike, curable, thermootclaim 4.

plastic linear polyester 'prepared'lby the process of claim 1:

6. A new composition oi matter comprising a miliable, moldable,crumblike, curable, thermoplastic lineslr polyester prepared by theprocess 0! claim 2.9

7. A new composition of matter comprising a millable, moldable,crumblike, curable, thermoplastic linear polyester prepared by theprocess of claim 3.

8. A new composition of matter comprising a millable, moldable,crumbllke, curable, thermoplastic linear polyester prepared by theprocess mmNG'roN M. BEAVERS.

;,REFERENCES CITED UNITED STATES PATENTS Number Name a Date 2,322,756Wallder June 29, 1943 2,363,581 Frosch Nov. 28, 1944 5 2,418,282 BiggsFeb. 25, 1947 OTHER REFERENCES 1.5 J. M. Ball (P886 2'75).

The following references are oi record in the file o t this patent:

